It has long been known that a problem exists with regard to the backing up of a trailer or other type of towable vehicle. This problem exists with regard to two-wheeled single axle trailers, as well as four-wheeled double axle trailers. The average driver not familiar with or experienced in the handling of trailers has a great deal of trouble in controlling the directional movements of the trailer, while attempting to back up his or her vehicle and trailer.
In order to insure that the standard trailer properly follows or tracks the towing vehicle, the spindles upon which the wheel hubs rotate are normally positioned behind the kingpins. This configuration provides for better tracking of the trailer through turns when moving in a forward direction. This same configuration, however, is known to inhibit the ability of the trailer to be easily and properly directed during the backing up or rearward movement of the vehicle.
Various prior art devices have attempted to solve this problem by providing for a shifting of the placement or castering of the spindle, from behind the kingpin during forward movement to a position in front of the kingpin during rearward or reverse movement of the vehicle. These devices have traditionally relied upon a friction mechanism to momentarily lock the wheel while the shifting or transfer of the axle caster took place. Examples of such types of devices are described in Morita, U.S. Pat. No. 4,494,272, Barchus, U.S. Pat. No. 3,883,151 and Linn, U.S. Pat. No. 1,915,325. These devices all suffer from a lack of preciseness in their automatic shifting action. These devices utilize a moving component which is frictionally engaged within the wheel assembly to momentarily lock the wheel in place allowing for a pivoting of the spindle about the kingpin. The locking ability of such devices depends, in part, upon the suddenness or force of the initial rearward movement of the trailer and the condition of the components. Due to the wear of the components resulting from the frictional locking movement, as the components age the locking capabilities of the mechanism change over time.
Prior devices, such as those just described, have primarily been utilized on two-wheeled or single-axle trailers. Such devices have not generally proven satisfactory for use on four-wheeled or double-axle trailers. Up to this point, a satisfactory means for enhancing the control of a double-axled trailer during backing-up has not existed. Various devices have been developed to improve the steerability of double-axled trailers so that they will more properly follow the towing vehicle through turns while being pulled forward. An example of such a device is shown in Watson, U.S. Pat. No. 3,876,240. This type of device, however, does not provide for the improved handling of the double-axled trailer when the trailer is being backed up.
A need, therefore, exists for an improved automatic self-steering axle for trailers and other towable vehicles to improve the ability of the vehicle to be controlled while being backed up or otherwise moved in a rearward direction.